a0006 linq to objects using c 4 morebook vn 244

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U SING AND E XTENDING LINQ TO

O BJECTS AND P ARALLEL LINQ (PLINQ)

Troy Magennis

Upper Saddle River, NJ • Boston • Indianapolis • San Francisco

New York • Toronto • Montreal • London • Munich • Paris • Madrid

Capetown • Sydney • Tokyo • Singapore • Mexico City

Many of the designations used by manufacturers and sellers to distinguish their products are claimed

as trademarks Where those designations appear in this book, and the publisher was aware of a

trade-mark claim, the designations have been printed with initial capital letters or in all capitals

The author and publisher have taken care in the preparation of this book, but make no expressed or

implied warranty of any kind and assume no responsibility for errors or omissions No liability is

assumed for incidental or consequential damages in connection with or arising out of the use of the

information or programs contained herein

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Library of Congress Cataloging-in-Publication Data:

Magennis, Troy,

1970-LINQ to objects using C# 4.0 : using and extending 1970-LINQ to objects and parallel 1970-LINQ (P1970-LINQ) /

Troy Magennis

p cm

Includes bibliographical references and index

ISBN 978-0-321-63700-0 (pbk : alk paper) 1 Microsoft LINQ 2 Query languages (Computer

sci-ence) 3 C#

(Computer program language) 4 Microsoft NET Framework I Title

QA76.73.L228M345 2010

006.7’882—dc22

2009049530 Copyright © 2010 Pearson Education, Inc

All rights reserved Printed in the United States of America This publication is protected by copyright,

and permission must be obtained from the publisher prior to any prohibited reproduction, storage in a

retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying,

recording, or likewise For information regarding permissions, write to:

Pearson Education, Inc

Rights and Contracts Department

501 Boylston Street, Suite 900

Boston, MA 02116

Fax (617) 671 3447

ISBN-13: 978-0-321-63700-0

ISBN-10: 0-321-63700-3

Text printed in the United States on recycled paper at RR Donnelly in Crawfordsville, Indiana

First printing March 2010

To my wife, Janet Doherty, for allowing me to spend those

extra hours tapping away on the keyboard; thank you for

your support and love.

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Query Expressions, 29-30

query operators, 121

aggregation operators

Aggregate operator, 123-125

Average operator, 126-129

Count operator, 129-131

LongCount operator,

129-131

Max operator, 126-129

Min operator, 126-129

Sum operator, 126-129

writing, 216-222

conversion operators

AsEnumerable, 133

Cast, 133-134

OfType, 134-136

ToArray, 136

ToDictionary, 136-139

ToList, 140

ToLookup, 140-143

element operators

DefaultlfEmpty, 144-145

ElementAt, 145-147

ElementAtOrDefault,

145-147

First, 147-149

FirstOrDefault, 147-149

Last, 149-151

LastOrDefault, 149-151

Single, 151-153

SingleOrDefault, 151-153

grouping operators, writing,

222-232

sequence operators

TakeRange, building,

210-216

writing, 208-216

single element operators,

writing, 196-208

R

race conditions, 265-266

RandomElement operator,

building, 201-208

Range operator, 156-158

range partitioning, 277

Repeat operator, 158-159

Index 311

return type, changing, 54 anonymous type, returning, 58-59

different type as source, returning, 56-58 grouped objects, returning, 59 same type as source,

returning, 56 single result value, returning, 55 returning sequenced elements with SelectMany operator, 59-61 reversing query result order, 65 row iterator, building in Microsoft Excel, 256-260 Rusina, Alexandra, 200

S

Segment operator, building, 226-232

selecting query syntax, 42 selection projections query return type, changing, 54-55

anonymous type, returning, 58-59

different type as source, returning, 56-58 grouped objects, returning, 59 same type as source, returning, 56 single result value, returning, 55 SelectMany operator, 59-61 sequence operators TakeRange, building, 210-216 writing, 208-216

SequenceEqual operator, 154-155

sequences returning, 59-61 single element operators Last, building, 196-201 RandomElement, building, 201-208

writing, 196-208

Single operator, 151-153 SingleOrDefault operator, 151-153

one-to-one joins, 105-106 Skip operator, 161-162 SkipWhile operator, 163-164 sorting query results case in-sensitive string ordering, 65-67 cultural-specific string ordering, 65-67 custom sort comparison functions, specifying, 67-72

reversing result sequence, 65 syntax, 63-64

Soundex equality operator, building, 84-87 Standard Query Operators, 14 striped partitioning, 278 subqueries

one-to-many joins, performing, 115-116

one-to-one joins, performing, 104-105

Sum operator, 126, 128-129 summarizing data from two collections, comparing LINQ and C# 2.0 approaches, 8-12 synchronization, 269 syntax

LINQ to Objects query examples, 30-38 queries

choosing, 42 methods, comparing, 45-49 query expression format, 43-45

results, sorting, 63-64

T

Take operator, 161-162 TakeRange operator, building, 210-216

TakeWhile operator, 163-164 ternary operators, 79

testing Parallel LINQ operators,

295-297

this modifier, 18

thread-level parallelism, 264

threading, 264

ToArray operator, 136

ToDictionary operator, 136-139

ToList operator, 140

ToLookup operator, 140-143

one-to-many joins, performing,

116-117

Toub, Stephen, 278

two-source operators, 287-289

U–V

Union operator, 181-183

unstable sorting types, 64

Visual Studio, adding

COM-Interop interfaces,

255-256

W

Where clause

query expression syntax, 51

query results, filtering, 49-50

by index position, 53-54

deferred execution, 51

with external method for

evaluation, 52-53

writing

grouping operators, 222-232

Min Operator, 216-219

Parallel LINQ operators,

289-294

query operators, grouping

operators, 222-232

sequence operators, 208-216

single element operators,

196-208

XML, comparing LINQ and

C# 2.0 and 3.0

approaches, 8-12

312 Index

X–Y–Z

XML, comparing LINQ and C# 2.0 writing approaches, 8-12 Zip operator, 159-160